Insights into the microstructural evolution and ablation mechanism of HfCxN1−x ceramics subjected to extreme laser ablation

The laser ablation mechanism of PDC-SPS HfC x N 1 − x ceramics was clarified. • At 39.8 MW m –2 heat flux, HfC 0.75 N 0.25 shows superior ablation resistance. • Dislocations, lath-like structures and dense Hf(C,N,O) layers stabilize ablation. Hafnium carbonitride (HfC x N 1− x ) ceramics show great potential for thermal protection systems due to their ultra-high melting point, and investigating their ablation behavior is essential for their application under extreme conditions. In this work, HfC x N 1− x ceramics with varying nitrogen contents were synthesized via polymer-derived ceramic followed by spark plasma sintering. Laser ablation tests showed that HfC 0.75 N 0.25 achieved excellent ablation resistance under the laser power of 500 W, with linear and mass ablation rates of 1.08 µm s −1 and 0.32 mg s −1 , respectively. This is ascribed to the high melting point and exceptional thermal stability of HfC 0.75 N 0.25 , which result from moderate nitrogen incorporation. During laser ablation, dislocation accumulation and the formation of lath-like structures dissipate part of the laser heat flux. Subsequently, a dense Hf(C, N, O) solid solution layer with high viscosity forms, which effectively impedes oxygen diffusion and maintains stable ablation resistance of HfC 0.75 N 0.25 . Conversely, excessive nitrogen incorporation induces the formation of the Hf 7 O 8 N 4 phase with numerous defects and crack nucleation, ultimately deteriorating laser ablation resistance. These findings provide useful insights for the design and development of ultra-high temperature ceramics for applications in extreme environments. Download: Download high-res image (277KB) Download: Download full-size image